A low thermal conductivity, high reflectivity composite coating and method of manufacture

Abstract

The application provides a low-thermal-conductivity and high-reflectivity composite coating and a preparation method, the composite coating system has a double-layer ceramic layer structure, the bottom ceramic layer is an 8YSZ ceramic, and the top ceramic layer is a ceramic with high reflectivity to thermal radiation infrared spectrum, and mainly has three component systems: (1) HfO2+Gd2Zr2O7+SCSZ system; (2) LZO+LCO+GYbZ system; (3) mullite+cordierite+aluminate system. Since the outermost ceramic layer has high infrared reflectivity, the heat insulation performance of the thermal barrier coating can be greatly improved. Meanwhile, the atmospheric laminar plasma torch is used for preparing the ceramic coating, and the ceramic coating with high-density through vertical crack structure can be prepared, and the thermal cycle life of the thermal barrier coating can be significantly improved.

Description

Technical Field

[0001] This invention relates to the field of composite coating technology, and in particular to a low thermal conductivity, high reflectivity composite coating and its preparation method. Background Technology

[0002] High-temperature alloys, with their excellent high-temperature mechanical properties, oxidation resistance, and corrosion resistance, are widely used in gas turbines, thermal power generation, and the nuclear energy industry. However, with the development of aerospace engine and gas turbine technology, the requirements for engineering structural materials in high-temperature working environments are becoming increasingly stringent. Currently, the temperature of gas combustion gases is approaching 2000K, significantly higher than the melting point of high-temperature alloys (approximately 1300℃). Therefore, high-temperature alloys can no longer fully meet the application requirements. To adapt to harsh high-temperature working environments, surface modification of high-temperature alloys has become necessary.

[0003] Thermal barrier coatings are functional coatings that provide thermal insulation. They typically involve applying a high-melting-point material with low thermal conductivity to the surface of hot-end components, preventing the direct contact of high-temperature media with the metal substrate. This acts as a barrier against the heating of the metal substrate by the high-temperature medium, thus protecting the alloy substrate by reducing the surface temperature of the metal component. Currently used thermal barrier coating systems mainly consist of a three-layer structure: the metal substrate to be protected, an adhesive layer, and a ceramic layer. There are three main methods for preparing the ceramic layer: plasma spraying (APS), electron beam physical vapor deposition (EB-PVD), and plasma spraying physical vapor deposition (PS-PVD). The adhesive layer is primarily composed of Ni-Al based and MCrAlY based materials. A continuous Al2O3 layer is formed in a high-temperature environment to protect the metal substrate. Because the Al2O3 layer is sufficiently dense, it forms a protective film that prevents oxygen from diffusing into the substrate and causing oxidation and failure of the substrate material. The outermost ceramic coating mainly serves as a heat insulation material. 8YSZ material is usually used as the heat insulation coating material. A 150μm thick ceramic coating can reduce the surface temperature of the substrate by 100-150℃.

[0004] Coatings prepared using the APS method exhibit a typical layered structure. Although the high porosity results in low thermal conductivity, the thermal cycle life of the coating is also very low. Coatings prepared using the EB-PVD and PS-PVD methods exhibit a typical columnar structure, and their thermal cycle life is significantly higher than that of coatings prepared using APS. However, both of these methods require vacuum conditions, leading to higher production costs. Meanwhile, the continuously increasing internal temperature of aero-engine combustion chambers places higher demands on the thermal insulation performance of thermal barrier coatings. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention provides a low thermal conductivity, high reflectivity composite coating and its preparation method. By designing and preparing a low thermal conductivity, high reflectivity, double-layer ceramic protective coating material, the thermal barrier coating's insulation capability and thermal service life above 1000℃ are improved. The specific invention details are as follows:

[0006] In a first aspect, the present invention provides a method for preparing a composite coating with low thermal conductivity and high reflectivity, the method comprising the following preparation steps:

[0007] S1. NiCoCrAlY alloy powder is sprayed onto the surface of the alloy substrate using plasma spraying, supersonic flame spraying, laser cladding equipment or arc cladding equipment to form a Ni-based bonding layer.

[0008] S2. 8YSZ powder is prepared on the surface of the Ni-based adhesive layer by atmospheric laminar plasma spraying or electron beam physical vapor deposition technology to form a first ceramic coating.

[0009] S3. Further, HfO2+Gd2Zr2O7+SCSZ combined powder, LZO+LCO+GybZ combined powder, or aluminate+mullite+cordierite combined powder are prepared on the surface of the first ceramic coating by atmospheric laminar plasma spraying or electron beam physical vapor deposition technology to form a second ceramic coating.

[0010] Optionally, in step S1, the thickness of the Ni-based adhesive layer is 1-150 μm.

[0011] Optionally, in step S2, the particle size of the 8YSZ powder is 37-69 μm.

[0012] Optionally, in step S2, the powder feeding rate of the 8YSZ powder is 3-4 g / min.

[0013] Optionally, the thickness of the first ceramic coating is 200-300 μm;

[0014] The microstructure of the first ceramic coating has a vertical crack structure with a density of 2-4 cracks per millimeter.

[0015] Optionally, the thickness of the second ceramic coating is 150-200 μm;

[0016] The microstructure of the second ceramic coating has a vertical crack structure with a density of 2-4 cracks per millimeter.

[0017] Optionally, the operating parameters of the atmospheric laminar plasma spraying technology are:

[0018] The volume ratio of nitrogen to argon is 7:3;

[0019] The operating current is 120-160A;

[0020] Output power is 15-30kW;

[0021] The spraying distance is 200-300mm;

[0022] The spraying speed is 0.4-0.8 m / s;

[0023] The spraying interval is 3-8mm.

[0024] Optionally, the operating parameters of the atmospheric laminar plasma spraying technology are:

[0025] The volume ratio of nitrogen to argon is 7:3;

[0026] The operating current is 160A;

[0027] The output power is 25-26kW;

[0028] The spraying distance is 250mm;

[0029] The spraying speed is 0.4 m / s;

[0030] The spraying interval is 4mm.

[0031] Optionally, the alloy matrix includes: heat-resistant stainless steel 310S, high-temperature alloy K456, Incoloy M956, or DZ640M.

[0032] Optionally, the alloy substrate surface is an alloy substrate surface that has undergone degreasing and sandblasting treatment.

[0033] In a second aspect, the present invention provides a low thermal conductivity, high reflectivity composite coating obtained by the preparation method described in the first aspect above. The composite coating material comprises: an adhesive layer, a first ceramic coating, and a second ceramic coating sequentially located on the surface of an alloy substrate.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] This invention provides a low thermal conductivity, high reflectivity thermal barrier coating material and its preparation method that are prepared under atmospheric conditions and have a long thermal cycling life. The thermal barrier coating system has a double-layer ceramic structure. The bottom ceramic layer is 8YSZ ceramic, and the top ceramic layer is a ceramic with high reflectivity to the infrared spectrum of thermal radiation. It mainly consists of three component systems: (1) HfO2+Gd2Zr2O7+SCSZ system; (2) LZO+LCO+GYbZ system; (3) Mullite+Cordierite+Aluminate system. Due to the high infrared reflectivity of the outermost ceramic layer, it can significantly improve the thermal insulation performance of the thermal barrier coating. At the same time, an atmospheric laminar flow plasma spray gun is used to prepare the ceramic coating, which can prepare a ceramic coating with a high-density through-crack structure. This structure can significantly improve the thermal cycling life of the thermal barrier coating. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 A schematic diagram of the preparation method of the low thermal conductivity and high reflectivity composite coating provided in the embodiment of the present invention is shown;

[0038] Figure 2 A schematic diagram of the low thermal conductivity, high reflectivity composite coating provided in an embodiment of the present invention is shown.

[0039] Figure 3 A cross-sectional topography diagram of a low thermal conductivity, high reflectivity composite coating provided in an embodiment of the present invention is shown. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0041] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0042] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0043] In the description of this invention, it should be understood that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0044] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0045] In a first aspect, the present invention provides a method for preparing a composite coating with low thermal conductivity and high reflectivity. Figure 1 This diagram illustrates a process flow chart for preparing a low thermal conductivity, high reflectivity composite coating according to an embodiment of the present invention. Figure 1 As shown, the preparation method includes the following preparation steps:

[0046] S1. NiCoCrAlY alloy powder is sprayed onto the surface of the alloy substrate using plasma spraying, supersonic flame spraying, laser cladding equipment or arc cladding equipment to form a Ni-based bonding layer.

[0047] S2. 8YSZ powder is prepared on the surface of the Ni-based adhesive layer by atmospheric laminar plasma spraying or electron beam physical vapor deposition technology to form a first ceramic coating.

[0048] S3. Further, HfO2+Gd2Zr2O7+SCSZ combined powder, LZO+LCO+GybZ combined powder, or aluminate+mullite+cordierite combined powder are prepared on the surface of the first ceramic coating by atmospheric laminar plasma spraying or electron beam physical vapor deposition technology to form a second ceramic coating.

[0049] In specific implementation, this invention discloses a low thermal conductivity, high reflectivity composite coating and its preparation method. In the preparation solution provided by this invention, the adhesive layer uses NiCoCrAlY alloy powder, and the ceramic layer adopts a double-layer composite structure. The bottom ceramic layer is 8YSZ, and the top ceramic layer is a 1:1:1 HfO2+Gd2Zr2O7+SCSZ system, a 1:1:1 LZO+LCO+GYbZ system, or a 1:1:1 mullite+cordierite+aluminate system. The specific preparation steps are as follows:

[0050] Step 1: Mix the powders involved in the HfO2+Gd2Zr2O7+SCSZ system, LZO+LCO+GYbZ system and mullite+cordierite+aluminate system according to a certain mass ratio (1:1:1) and mix them evenly by mechanical mixing.

[0051] Step 2: Degrease and sandblast the high-temperature alloy to obtain a high-temperature alloy surface with a certain roughness.

[0052] Step 3: Prepare a NiCoCrAlYNi-based bonding layer on a high-temperature alloy substrate using plasma spraying, supersonic flame spraying, laser cladding, or arc cladding equipment. The thickness of the bonding layer is 1-150μm.

[0053] Step 4: On the surface of the adhesive layer prepared in step 3, a ceramic layer is prepared by atmospheric laminar flow plasma spraying. The material composition of this ceramic layer is 8YSZ. By controlling the spraying parameters, an 8YSZ ceramic layer with a thickness of approximately 200μm is prepared on the adhesive layer.

[0054] Step 5: Based on the 8YSZ ceramic coating obtained in Step 4, the outermost ceramic coating is prepared by atmospheric laminar plasma spraying. The coating type is one of the following: HfO2+Gd2Zr2O7+SCSZ system, LZO+LCO+GYbZ system, and mullite+cordierite+aluminate system. The coating thickness is approximately 100μm.

[0055] Figure 2 A schematic diagram of the low thermal conductivity, high reflectivity composite coating provided in an embodiment of the present invention is shown, as follows: Figure 2 As shown, the composite coating material includes: an adhesive layer 102, a first ceramic coating 103, and a second ceramic coating 104, which are sequentially located on the surface of the alloy substrate 101.

[0056] The thermal barrier coating prepared by this method has a double-layer ceramic composite structure. The outermost ceramic layer has high reflectivity, resulting in better thermal insulation performance. Simultaneously, the double ceramic layer prepared by atmospheric laminar plasma spraying exhibits a high density of through-cracks, leading to a longer thermal cycling life. In summary, this method can produce thermal barrier coatings with both superior thermal insulation performance and longer thermal cycling life.

[0057] To enable those skilled in the art to better understand this application, the following embodiments will be used to provide a detailed description of a low thermal conductivity, high reflectivity composite coating and its preparation method.

[0058] Example 1: Spraying HfO2+Gd2Zr2O7+SCSZ coating onto the surface of heat-resistant stainless steel 310S

[0059] Heat-resistant stainless steel 310S is an austenitic stainless steel with excellent oxidation resistance and corrosion resistance. Due to its high percentage of chromium and nickel, it has good creep strength and can operate continuously at high temperatures, exhibiting good high-temperature resistance.

[0060] 1) Prepare the base material and fix it in place using a fixing clamping device.

[0061] 2) After surface sandblasting, the NiCoCrAlY bonding layer is first sprayed with supersonic flame to obtain a coating with a thickness of 150μm.

[0062] 3) Use 8YSZ powder with a particle size of 37-69μm and a powder feeding rate of 3-4g / min.

[0063] 4) Turn on the atmospheric laminar plasma control device and plasma generation device.

[0064] 5) Adjust the working gas to nitrogen and argon with a volume ratio of 7:3 using a long jet control device, with a working current of 160A and an output power of 25-26kW.

[0065] 6) Select a spraying distance of 250mm, a scanning speed of 0.4m / s, and a scanning interval of 4mm.

[0066] 7) By controlling the robotic arm and spraying the coating 20 times in a cycle, a first ceramic coating with a thickness of about 200μm can be obtained.

[0067] 8) First, turn off the powder feeding control unit, then turn off the plasma generator generating unit, and finally turn off the plasma generator circulating water device.

[0068] 9) Replace the 8YSZ ceramic powder in the powder feeder with HfO2+Gd2Zr2O7+SCSZ powder with a particle size of 50-80μm, and repeat steps (4)-(6).

[0069] 10) By controlling the robotic arm and spraying the coating 10 times in a cycle, a second ceramic coating with a thickness of about 100μm can be obtained.

[0070] 11) First, turn off the powder feeding control unit, then turn off the plasma generator generating unit, and finally turn off the plasma generator circulating water device.

[0071] 12) Wait for the substrate temperature control unit to lower the sample temperature to room temperature, then remove the sample to obtain a low thermal conductivity, high reflectivity composite coating.

[0072] Figure 3 The cross-sectional morphology diagram of the low thermal conductivity, high reflectivity composite coating provided in the embodiment of the present invention is shown, as follows: Figure 3 As shown, the low thermal conductivity, high reflectivity composite coating has vertical through cracks.

[0073] Example 2: LZO+LCO+GYbZ coating sprayed onto the surface of high-temperature alloy K456

[0074] Nickel-based superalloy K465 alloy has high resistance to creep and fatigue and high temperature resistance.

[0075] 1) Prepare the matrix material It is fixed to the substrate temperature control unit by a fixing clamping device.

[0076] 2) After surface sandblasting, a Ni-60%Ti-0.3%Hf coating is first applied by plasma spraying to obtain a 150μm thick adhesive layer.

[0077] 3) Use 8YSZ powder with a particle size of 37-69μm and a powder feeding rate of 3-4g / min.

[0078] 4) Turn on the plasma control device and plasma generation device.

[0079] 5) The working gas is adjusted to nitrogen and argon with a volume ratio of 7:3 through the long jet control device, the working current is 160A and the output power is 25-26kW.

[0080] 6) Select a spraying distance of 250mm, a scanning speed of 0.4m / s, and an interval of 4mm.

[0081] 7) By controlling the robotic arm and spraying the coating 10 times in a cycle, a first ceramic coating with a thickness of more than 200μm can be obtained.

[0082] 8) First, turn off the powder feeding control unit, then turn off the plasma generator generating unit, and finally turn off the plasma generator circulating water device.

[0083] 9) Replace the 8YSZ ceramic powder in the powder feeder with LZO+LCO+GYbZ powder with a particle size of 60-90μm, and repeat steps (4)-(6).

[0084] 10) By controlling the robotic arm and spraying the coating 10 times in a cycle, a second ceramic coating with a thickness of about 100μm can be obtained.

[0085] 11) First, turn off the powder feeding control unit, then turn off the plasma generator generating unit, and finally turn off the plasma generator circulating water device.

[0086] 12) Wait for the substrate temperature control unit to lower the sample temperature to room temperature, remove the sample, and obtain a low thermal conductivity, high reflectivity composite coating with vertical through cracks.

[0087] The low thermal conductivity and high reflectivity composite coating prepared in this embodiment has a similar cross-sectional morphology to that of Example 1, and will not be repeated here.

[0088] Example 3: Incoloy M956 surface coated with a mullite + cordierite + aluminate coating

[0089] M956 alloy has high creep strength and excellent resistance to oxidation and corrosion at high temperatures. It is widely used as a hot-end component in advanced aero-engines with operating temperatures of 1000-1200℃ and as a thermal protection component in industrial furnaces with temperatures exceeding 1300℃.

[0090] 1) Prepare the substrate material and fix it to the substrate temperature control unit using a fixing clamping device. After surface sandblasting, first use laser cladding to apply a Ni-35%Ti-1%Zr coating to obtain a 100μm thick adhesive layer.

[0091] 2) Use 8YSZ powder with a particle size of 37-69μm and a powder feeding rate of 3-4g / min.

[0092] 3) Turn on the plasma control device and plasma generation device.

[0093] 4) The working gas is adjusted to nitrogen and argon with a volume ratio of 7:3 using a long jet control device. The working current is 160A and the output power is 25-26kW.

[0094] 5) Select a spraying distance of 250mm, a scanning speed of 0.4m / s, and an interval of 4mm.

[0095] 6) By controlling the robotic arm and spraying 20 times in a cycle, a first ceramic coating with a thickness of more than 200μm can be obtained.

[0096] 7) First, turn off the powder feeding control unit, then turn off the plasma generator generating unit, and finally turn off the plasma generator circulating water device.

[0097] 8) Replace the 8YSZ ceramic powder in the powder feeder with mullite + cordierite + aluminate powder with a particle size of 60-90μm, and repeat steps (4)-(6).

[0098] 9) By controlling the robotic arm and spraying the coating 10 times in a cycle, a second ceramic coating with a thickness of about 100μm can be obtained.

[0099] 10) First, turn off the powder feeding control unit, then turn off the plasma generator generating unit, and finally turn off the plasma generator circulating water device.

[0100] 11) Wait for the substrate temperature control unit to lower the sample temperature to room temperature, remove the sample, and obtain a low thermal conductivity, high reflectivity composite coating with vertical through cracks.

[0101] The low thermal conductivity and high reflectivity composite coating prepared in this embodiment has a similar cross-sectional morphology to that of Example 1, and will not be repeated here.

[0102] Example 4: Spraying HfO2+Gd2Zr2O7+SCSZ coating onto the surface of DZ640M

[0103] DZ640M (DZ40M) is a cobalt-based precipitation-hardening, directionally solidified columnar superalloy with an operating temperature below 1040℃. This alloy exhibits stable microstructure and excellent resistance to thermal fatigue, oxidation, and hot corrosion. It also demonstrates good overall performance in terms of creep resistance, endurance, and fatigue resistance. Its main products include directionally solidified castings such as turbine guide vanes.

[0104] 1) Prepare a substrate material of 8×200×200mm, fix it to the substrate temperature control unit with a fixing clamping device, and use an arc cladding device to clad a 100μm Ni-30%Ti-0.5%Y layer on the substrate surface.

[0105] 2) Use 8YSZ powder with a particle size of 37-69μm and a powder feeding rate of 3-4g / min.

[0106] 3) Turn on the plasma control device and plasma generation device.

[0107] 4) The working gas is adjusted to nitrogen and argon with a volume ratio of 7:3 using a long jet control device. The working current is 160A and the output power is 25-26kW.

[0108] 5) Select a spraying distance of 250mm, a scanning speed of 0.4m / s, and an interval of 4mm.

[0109] 6) By controlling the robotic arm, a coating with a thickness of more than 200μm can be obtained by spraying 20 times in a cycle.

[0110] 7) First, turn off the powder feeding control unit, then turn off the plasma generator generating unit, and finally turn off the plasma generator circulating water device.

[0111] 8) Replace the 8YSZ ceramic powder in the powder feeder with HfO2+Gd2Zr2O7+SCSZ powder with a particle size of 50-80μm, and repeat steps (4)-(6).

[0112] 9) By controlling the robotic arm and spraying the coating 10 times in a cycle, a coating thickness of about 100μm can be obtained.

[0113] 10) First, turn off the powder feeding control unit, then turn off the plasma generator generating unit, and finally turn off the plasma generator circulating water device.

[0114] 11) Wait for the substrate temperature control unit to lower the sample temperature to room temperature, remove the sample, and obtain a low thermal conductivity, high reflectivity composite coating with vertical through cracks.

[0115] The low thermal conductivity and high reflectivity composite coating prepared in this embodiment has a similar cross-sectional morphology to that of Example 1, and will not be repeated here.

[0116] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0117] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0118] The present invention provides a detailed description of a low thermal conductivity, high reflectivity composite coating and its preparation method. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing a composite coating with low thermal conductivity and high reflectivity, characterized in that, The preparation method includes the following preparation steps: S1. NiCoCrAlY alloy powder is sprayed onto the surface of the alloy substrate using plasma spraying, supersonic flame spraying, laser cladding equipment or arc cladding equipment to form a Ni-based bonding layer. S2. 8YSZ powder is prepared on the surface of the Ni-based adhesive layer by atmospheric laminar plasma spraying or electron beam physical vapor deposition technology to form a first ceramic coating. S3. Further, HfO2 + Gd2Zr2O7 + SCSZ combined powder, LZO + LCO + GYbZ combined powder or aluminate + mullite + cordierite combined powder are prepared on the surface of the first ceramic coating by atmospheric laminar plasma spraying or electron beam physical vapor deposition technology to form a second ceramic coating. In the second ceramic coating, the mass ratio of HfO2+Gd2Zr2O7+SCSZ is 1:1:1, the mass ratio of LZO+LCO+GYbZ is 1:1:1, and the mass ratio of mullite+cordierite+aluminate is 1:1:

1. The thickness of the second ceramic coating is 150-200 μm; The microstructure of the second ceramic coating has a vertical crack structure with a density of 2-4 cracks per millimeter.

2. The method for preparing the low thermal conductivity, high reflectivity composite coating according to claim 1, characterized in that, In step S1, the thickness of the Ni-based adhesive layer is 1-150 μm.

3. The method for preparing the low thermal conductivity, high reflectivity composite coating according to claim 1, characterized in that, In step S2, the particle size of the 8YSZ powder is 37-69 µm; The powder feeding rate of the 8YSZ powder is 3~4 g / min.

4. The method for preparing the low thermal conductivity, high reflectivity composite coating according to claim 1, characterized in that, In step S2, the thickness of the first ceramic coating is 200-300 μm; The microstructure of the first ceramic coating has a vertical crack structure with a density of 2-4 cracks per millimeter.

5. The method for preparing the low thermal conductivity, high reflectivity composite coating according to claim 1, characterized in that, The operating parameters of the atmospheric laminar plasma spraying technology are as follows: The volume ratio of nitrogen to argon is 7:3; The operating current is 120-160A; Output power is 15-30 kW; The spraying distance is 200-300 mm; The spraying speed is 0.4-0.8 m / s; The spraying interval is 3-8 mm.

6. The method for preparing the low thermal conductivity, high reflectivity composite coating according to claim 1, characterized in that, The operating parameters of the atmospheric laminar plasma spraying technology are as follows: The volume ratio of nitrogen to argon is 7:3; The operating current is 160A; Output power is 25-26 kW; The spraying distance is 250 mm; The spraying speed is 0.4 m / s; The spraying interval is 4 mm.

7. The method for preparing the low thermal conductivity, high reflectivity composite coating according to claim 1, characterized in that, The alloy matrix includes: heat-resistant stainless steel 310S, high-temperature alloy K456, Incoloy MA956 or DZ640M.

8. The method for preparing the low thermal conductivity, high reflectivity composite coating according to claim 1, characterized in that, The surface of the alloy substrate is the surface of the alloy substrate after degreasing and sandblasting treatment.

9. A low thermal conductivity, high reflectivity composite coating obtained by the preparation method according to any one of claims 1-8.

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